WO2008061826A1

WO2008061826A1 - Method for the production of synthetic polyethylene waxes with high crystallinity and low viscosity

Info

Publication number: WO2008061826A1
Application number: PCT/EP2007/059614
Authority: WO
Inventors: Volker Schrenk; Udo Spitzer; Hans-Dieter Zagefka
Original assignee: Evonik Degussa Gmbh
Priority date: 2006-11-25
Filing date: 2007-09-13
Publication date: 2008-05-29
Also published as: US9403923B2; TW200844115A; CN101589072B; TWI481622B; CN101589072A; EP2097462A1; US20100050900A1; DE102006055729A1

Abstract

A method for the production of a polyethylene wax by the polymerization of ethylene in the presence of a Ziegler-Natta catalyst system which is composed of titanium tetrachloride and dialkylaluminum halide, wherein (the polymerization temperature lies in the range of 170 °C to 200 °C, the polymerization is carried out essentially in the absence of solvents, and the Al/Ti mole ratio is smaller than 1.6) a wax results with the following characteristics profile: - Ubbelohde melting point from 115 °C to 125 °C, - penetration value of maximum 1 mm · 10<SUP>-1</SUP>; - viscosity at 150 °C of less than 60 mPas; - density from 0.945 to 0.960 g/cm<SUP>3</SUP> at 23 °C; molar mass of less than 1500 g/mol, and - crystallinity of more than 70%.

Description

Process for the preparation of synthetic polyethylene waxes of high crystallinity and low viscosity

The invention relates to a method for producing highly crystalline and low-viscosity synthetic waxes from ethylene and the use of these waxes, for example in hotmelts or printing inks.

Synthetic waxes can be prepared, inter alia, by Ziegler-Natta polymerization of ethylene. In DE-OS 15 20 914 a process for the production of waxes from ethylene using the Ziegler-Natta synthesis is described. The polymerization, generally in gasoline as a solvent, at temperatures of 150 ⁰ C to 170 ⁰ C hard waxes and at temperatures of 170 ⁰ C to 190 ⁰ C soft waxes. In the examples described at polymerization temperatures of 150 ⁰ C to 170 ⁰ C products are described which are either higher viscosity and very hard (viscosities of more than 100 mPas at 150 ⁰ C and penetration numbers of less than 1 mm • 10 ^"1 at 23 ⁰ C) or low-viscosity and softer (about 50 mPas at 150 ⁰ C and more than 1 mm • 10 ^"1 at 23 ⁰ C). The properties of these polyethylene waxes produced according to the prior art are thus determined by the combination of viscosity and hardness. High hardnesses (less than 1 mm • 10 ^"1 ) can only be achieved at higher viscosities (more than 100 mPas), but this combination of properties is disadvantageous in some applications:

- Although corresponding micronized products have a good abrasion protection, but only low throughputs are obtained in the micronization;

- Although such products cause an excellent improvement in the heat resistance in hotmelts, but the viscosity of the hot melts is reduced only insufficient.

Fischer-Tropsch waxes, however, have in addition to a lower viscosity (less than 20 mPas at 150 ⁰ C) and a high hardness (penetration values of less than 1 mm • 10 ^"1) and are therefore particularly suitable for micronisation and for viscosity reduction of hotmelts However, the scuff protection effect is often insufficient and the improvement in the heat resistance of hot melts is lower than in the polyethylene waxes of the

DE-OS 15 20 914. The object of the present invention was to develop a process for the production of polyethylene waxes, in which the positive properties of higher-viscosity, hard polyethylene waxes are combined with the positive properties of Fischer-Tropsch waxes.

This object has been achieved by a process for producing a polyethylene wax by polymerization of ethylene in the presence of a Ziegler-Natta catalyst system composed of titanium tetrachloride and dialkylaluminum halide, wherein

the polymerization temperature is in the range from 170 to 200 ^° C., and preferably in the range from 175 to 195 ^° C.,

the polymerization is carried out essentially in the absence of solvent and

- The Al / Ti molar ratio is less than 1.6 and preferably less than 1.5.

Using this procedure, products with the following property profile are obtained:

Dropping point according to DIN 51801: 115 to 125 ⁰ C.

Penetration number according to DIN 51579: maximum 1 mm • 10 ^"1

Viscosity in accordance with DIN 52007/01: less than 60 mPas at 150 ⁰ C, preferably less than 50 mPas at 150 ⁰ C

Density: 0.945 to 0.960 g / cm ³ at 23 ⁰ C, preferably 0.950 to 0.960 g / cm ³ molecular weight (number average M _n from high temperature GPC according to ASTM D 6474-99: less than

1500 g / mol, preferably less than 1400 g / mol crystallinity (DSC analysis according to ISO 11357-3): greater than 70%

The invention furthermore relates to the polyethylene waxes which can be prepared by this process and to their use as additives for printing inks or coatings, constituents of hotmelts, expandable polystyrene nucleating agents or lubricants in PVC.

In the dialkylaluminum halide alkyl is preferably a group having 1 to 4 carbon atoms, for example methyl, ethyl, n-propyl, n-butyl or isobutyl, while as the halide, for example, chloride or bromide can be used. It is preferred Diethylaluminiumchlorid used.

Likewise provided by the present invention are printing inks, paints, powder coatings or hotmelts comprising polyethylene waxes according to the present invention. In the abovementioned applications, the polyethylene waxes according to the invention can be combined with all additives or auxiliaries known to the person skilled in the art and customary for these applications.

In the case of hotmelts, the polyethylene waxes of the present invention may be blended with, for example, polymers (e.g., polyolefins, amorphous polyalphaolefins, ethylene-vinyl acetate copolymers, synthetic rubber), resins (e.g., hydrocarbon and tall oil resins), and waxes (e.g. Fischer-Tropsch waxes, table paraffins).

Printing inks, coatings and powder coatings, in addition to the inventive polyethylene waxes additionally coloring agents, for example inorganic pigments (eg., Carbon black, TiO _2), effect pigments or organic pigments (eg. B. phthalocyanine, quinacridones) included. Further customary constituents are binders (for example: linseed oils, polyesters, phenolic resins, melamine resins, nitrocellulose, polyurethanes, epoxy resins, acrylates), solvents (for example hydrocarbons, alcohols, esters, water) and other additives (for example matting agents , Defoamer, leveling agent).

Even without further statements, it is assumed that a person skilled in the art can use the above description to the greatest extent. The preferred embodiments and examples are therefore to be considered as merely illustrative, in no way limiting, disclosure.

Hereinafter, the present invention will be explained in more detail by way of examples. Alternative embodiments of the present invention are obtainable in an analogous manner.

General procedure:

In a 20 m ³ reactor, which is equipped with a strong circulation pump, ethylene was continuously polymerized with the aid of the specified in Table 1 catalyst in the melt (10 m ³ polymer) with cooling. The gas composition at the beginning of the reaction was, depending on the product to be produced, according to GC analysis 35 to 70 vol. -% hydrogen, 30 to 50 vol .-% of ethylene, balance nitrogen. To remove the ethane formed during the polymerization, the gas was sucked out of the reactor chamber in certain cycles and burnt.

To determine the crystallinity, the enthalpy of fusion was first determined by DSC analysis in accordance with ISO 11357-3 during the second heating. From this, the crystallinity was calculated according to the following formula:

% Crystallinity = (ΔH _f - (AH _x ) / ΔH ° _f x 100%

with ΔH _t : area under the DSC melting curve, corresponds to the enthalpy of fusion of the polymer to be tested in J / g; ΔH _X : enthalpy for any crystallization of the polymer to be determined, which occurs during heating, in J / g (in the present case ΔH _X = 0 J / g); ΔH ° _f : Material-specific value for the enthalpy of fusion of a 100% crystalline one

Polymer, in this case (polyethylene) is ΔH ° _f = 286 J / g.

Comparative data of a commercial Fischer-Tropsch hard paraffin 2 ⁾ Comparative data of a commercially available higher crystalline polyethylene hard paraffin

Use of the wax according to the invention according to Example 1 and of the non-inventive Fischer-Tropsch hard paraffin according to Comparative Example 4 and the non-inventive Polvethylenhartparaffins according to Comparative Example 5 A. For printing inks The waxes were micronized in a commercial air jet mill at room temperature and a pressure of 7 bar; the result is shown in Table 2.

Throughput during micronization: wax from Bl 160 kg / h

Wax from VB 4 160 kg / h Wax from VB5 120 kg / h

Table 2: Grain size analysis (Malvern Mastersizer 2000)

Scrub resistance tests were carried out with 1% by weight wax addition in a commercially available toluene gravure printing ink and an offset printing ink using the Prüfbau-Quartant abrasion tester; see Table 3.

Table 3: Scheuerschutzprüfung

The wax of Example 1 according to the invention can be micronized under identical conditions with significantly higher throughputs than the wax according to Comparative Example 5, provides the same abrasion protection as the wax according to Comparative Example 5, but a significantly higher abrasion protection compared with the wax according to Comparative Example 4.

B. For hotmelts

Fischer-Tropsch waxes such. Example, the wax according to Comparative Example 4 are used to regulate the melt viscosity (ie, improve the processability) and the so-called "open time" (setting behavior) in hotmelts (often in combination with Table paraffins or microcrystalline waxes). They also improve the water vapor barrier effect, the surface smoothness and the appearance. In hotmelts based on EVA, however, the "Shear Adhesion Failure Temperature" (SAFT) is still to be improved.To improve the heat resistance, higher viscosity, highly crystalline waxes such as the wax from Comparative Example 5 are used, but here the reduction is The viscosity and surface smoothness often worse than when using Fischer-Tropsch waxes.With the waxes of the invention both high heat resistance and good surface smoothness and a reduction in viscosity similar to Fischer-Tropsch waxes can be achieved.

Test formulation:

1 part by weight EVA polymer (MFR 43 g / 10 min at 190 ° C / 2.16 kg,

VA content: 32% by weight) 1 parts by weight of tall resin ester 0.7 parts by weight of table paraffin 52/54 0.3 parts by mass of synthetic wax

Table 4: Results

C. Other applications

The wax according to the invention can advantageously also be used as a lubricant in PVC, as a nucleating agent for expandable polystyrene, as an additive for paints or powder coatings and as a starting material for the production of wax oxidate.

Claims

claims:

A process for producing a polyethylene wax by polymerization of ethylene in the presence of a Ziegler-Natta catalyst system composed of titanium tetrachloride and dialkylaluminum halide, wherein

the polymerization temperature is in the range from 170 to 200 ^° C.,

the polymerization is carried out essentially in the absence of solvent and

- The Al / Ti molar ratio is less than 1.6.

2. The method according to claim 1, characterized in that the polymerization temperature in the range of 175 to 195 ⁰ C.

3. The method according to claim 1 or 2, characterized in that the Al / Ti molar ratio is less than 1.5.

4. polyethylene wax, preparable according to one or more of claims 1 to 3.

5. polyethylene wax according to claim 4, characterized in that it has the following properties:

- Drop point according to DIN 51801 in the range of 115 to 125 ⁰ C;

- Penetration number according to DIN 51579 of max. 1 mm • 10 ^"1 ;

- Viscosity according to DIN 52007/1 at 150 ⁰ C of less than 60 mPas;

Density from 0.945 to 0.960 g / cm ³ at 23 ⁰ C;

- Molar mass (number average M _n from high-temperature GPC according to ASTM D 6474-99) of less than 1500 g / mol and

- crystallinity (DSC according to ISO 11357-3) of more than 70%.

6. polyethylene wax according to claim 4 or 5, characterized in that the viscosity at 150 ⁰ C is less than 50 mPas.

7. polyethylene wax according to one or more of claims 4 to 6, characterized in that the density is 0.950 to 0.960 g / cm ³ at 23 ⁰ C.

8. polyethylene wax according to one or more of claims 4 to 7, characterized in that the number average M _{n is} less than 1400 g / mol.

9. Use of the polyethylene wax according to one or more of claims 4 to 8 as an additive for printing inks, paints, powder coatings or hotmelts.

10. Use of the polyethylene wax according to one or more of claims 4 to 8 as nucleating agent for expandable polystyrene, lubricant in PVC or as starting material for the production of wax oxidate.

11. printing inks, paints, powder coatings or hotmelts containing polyethylene waxes according to one or more of claims 4 to 8.